Zero-Biased Photoelectrochemical Detection of Cardiac Biomarker Myoglobin Based on CdSeS/ZnS Quantum Dots and Barium Titanate Perovskite.

Cardiovascular diseases are considered one of the leading causes of premature mortality of patients worldwide. Therefore, rapid diagnosis of these diseases is crucial to ensure the patient's survival. During a heart attack or severe muscle damage, myoglobin is rapidly released in the body to constitute itself as a precise biomarker of acute myocardial infarction. Thus, we described the photoelectrochemical immunosensor development to detect myoglobin. It was based on fluorine-doped tin oxide modified with CdSeS/ZnSe quantum dots and barium titanate (BTO), designated as CdSeS/ZnSQDS/BTO. It was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and amperometry. The anodic photocurrent at the potential of 0 V (vs. Ag/AgCl) and pH 7.4 was found linearly related to the myoglobin (Mb) concentration from 0.01 to 1000 ng mL-1. Furthermore, the immunosensor showed an average recovery rate of 95.7-110.7% for the determination of myoglobin.

Evaluation of a photoelectrochemical platform based on strontium titanate, sulfur doped carbon nitride and palladium nanoparticles for detection of SARS-CoV-2 spike glycoprotein S1.

This work aims to develop a photoelectrochemical (PEC) platform for detection of SARS-CoV-2 spike glyprotein S1. The PEC platform is based on the modification of a fluorine-doped tin oxide (FTO) coated glass slide with strontium titanate (SrTiO3 or ST), sulfur-doped carbon nitride (g-C3N4-S or CNS) and palladium nanoparticles entrapped in aluminum hydroxide matrix (PdAlO(OH) or PdNPs). The PEC platform was denoted as PdNPs/CNS/ST/FTO and it was characterized by SEM, TEM, FTIR, DRX, and EIS. The PEC response of the PdNPs/CNS/ST/FTO platform was optimized by evaluating the effects of the concentration of the donor molecule, the nature of the buffer, pH, antibody concentration, potential applied to the working electrode, and incubation time. The optimized PdNPs/CNS/ST/FTO PEC platform was modified with 5 µg mL-1 of antibody for determination of SARS-CoV-2 spike glycoprotein S1. A decrease in the photocurrent was observed with an increase in the concentration of SARS-CoV-2 from 1 fg mL-1 to 1000 pg mL-1 showing that the platform is a promising alternative for the detection of S1 protein from SARS-CoV-2. The designed PEC platform exhibited recovery percentages of 96.20% and 109.65% in artificial saliva samples.

Applicability of a novel immunoassay based on surface plasmon resonance for the diagnosis of Chagas disease.

BACKGROUND: We defined the methodological criteria for the interpretation of the results provided by a novel immunoassay based on surface plasmon resonance (SPR) to detect antibodies anti-Trypanosoma cruzi in human sera (SPRCruzi). Then, we evaluated its applicability as a diagnostic tool for Chagas disease. METHODS: To define the cut-off point and serum dilution factor, 57 samples were analyzed at SPRCruzi and the obtained values of SPR angle displacement (ΔθSPR) were submitted to statistical analysis. Adopting the indicated criteria, its performance was evaluated into a wide panel of samples, being 99 Chagas disease patients, 30 non-infected subjects and 42 with other parasitic/infectious diseases. In parallel, these samples were also analyzed by ELISA. RESULTS: Our data demonstrated that 1:320 dilution and cut-off point at ∆θSPR=17.2 m° provided the best results. Global performance analysis demonstrated satisfactory sensitivity (100%), specificity (97.2%), positive predictive value (98%), negative predictive value (100%) and global accuracy (99.6%). ELISA and SPRCruzi showed almost perfect agreement, mainly between chagasic and non-infected individuals. However, the new immunoassay was better in discriminate Chagas disease from other diseases. CONCLUSION: This work demonstrated the applicability of SPRCruzi as a feasible, real time, label free, sensible and specific methodology for the diagnosis of Chagas disease.

Development of a label-free immunosensor based on surface plasmon resonance technique for the detection of anti-Leishmania infantum antibodies in canine serum.

In this work, a surface plasmon resonance (SPR) immunosensor was developed using an 11-mercaptoundecanoic acid (11-MUA) modified gold SPR sensor chip for the detection of anti-Leishmania infantum antibodies. The soluble antigens of L. infantum were securely immobilized on an SPR gold disk by an 11-MUA self-assembled monolayer. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) techniques were employed in the characterization of the antigen immobilization. After the immunosensor construction, canine serum positive for visceral leishmaniasis was added to its surface and showed significant variation in the SPR angle, indicating excellent sensitivity of the technique for antigen-antibody interaction detection. Moreover, the addition of negative serum was accompanied by a smaller response, demonstrating that the immunosensor shows good specificity against anti-L. infantum antibodies. Therefore, this work demonstrates the successful development of an SPR sensor for anti-L. infantum antibodies detection in short time, showing a great perspective as a sensing system of visceral leishmaniasis in endemic regions.

Dissolved oxygen amperometric sensor based on layer-by-layer assembly using host-guest supramolecular interactions.

The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using the host-guest binding of a supramolecular complex at a host surface by combining a self-assembled monolayer (SAM) of mono-(6-deoxy-6-mercapto)-beta-cyclodextrin (betaCDSH), iron (III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeTMPyP) and cyclodextrin-functionalized gold nanoparticles (CDAuNP). The supramolecular modified electrode showed excellent catalytic activity for oxygen reduction. The reduction potential of oxygen was shifted about 200 mV toward less negative values with this modified electrode, presenting a peak current much higher than those observed on a bare gold electrode. Cyclic voltammetry and rotating disk electrode (RDE) experiments indicated that the oxygen reduction reaction involves probably 4-electrons with a rate constant (k(obs)) of 7 x 10(4) mol(-1) Ls(-1). A linear response range from 0.2 up to 6.5 mg L(-1), with a sensitivity of 5.5 microA L mg(-1) (or 77.5 microA cm(-2) L mg(-1)) and a detection limit of 0.02 mg L(-1) was obtained with this sensor. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation was 3.0% for 10 measurements of a solution of 6.5 mg L(-1) oxygen.

Electrocatalysis of reduced L-glutathione oxidation by iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) adsorbed on multi-walled carbon nanotubes.

The development of a highly sensitive voltammetric sensor for reduced l-glutathione (GSH) using a basal plane pyrolytic graphite (BPPG) electrode modified with iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) adsorbed on multi-walled carbon nanotubes (MWCNT) is described. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to verify the morphologies and composition of the MWCNT after modification with the FeT4MPyP complex. The modified electrode showed very efficient electrocatalytic activity for l-glutathione oxidation, substantially decreasing the oxidation peak to -0.025V vs Ag/AgCl. A linear response range from 5 micromolL(-1) to 5 mmolL(-1) was obtained with a sensitivity of 703.41 microALmmol(-1). The detection limit for GSH determination was 0.5 micromolL(-1) and the relative standard deviation (R.S.D.) for 10 determinations of 250 micromolL(-1) GSH was 1.4%. The modified electrode was applied for GSH determination in erythrocyte samples and the results were in agreement to those obtained by a comparative method described in the literature.

Amperometric sensor for nitrite based on copper tetrasulphonated phthalocyanine immobilized with poly-L-lysine film.

In this work, an amperometric sensor for nitrite detection based on a glassy carbon electrode modified with copper tetrasulphonated phthalocyanine immobilized by polycationic poly-L-lysine film is presented. The modified electrode showed an excellent catalytic activity toward nitrite oxidation. A linear response range from 0.12 up to 12.20 micromol L(-1) was obtained with a sensitivity of 0.83 microA L micromol(-1). The detection limit for nitrite was 36 nmol L(-1). The repeatability of the proposed sensor, evaluated in terms of relative standard deviation, was 1% for 10 measurements of 10 micromol L(-1) nitrite solution. Finally, the developed sensor was applied for nitrite determination in water samples and the results were in agreement to the comparative method. The average recovery for the samples was 101 (+/-4)%.

A highly sensitive amperometric sensor for oxygen based on iron(II) tetrasulfonated phthalocyanine and iron(III) tetra-(N-methyl-pyridyl)-porphyrin multilayers.

The development of a highly sensitive sensor for oxygen is proposed using a glassy carbon (GC) electrode modified with alternated layers of iron(II) tetrasulfonated phthalocyanine (FeTsPc) and iron(III) tetra-(N-methyl-pyridyl)-porphyrin (FeT4MPyP). The modified electrode showed excellent catalytic activity for the oxygen reduction. The reduction potential of the oxygen was shifted about 330 mV toward less negative values with this modified electrode, presenting a peak current much higher than those observed on a bare GC electrode. Cyclic voltammetry and rotating disk electrode (RDE) experiments indicated that the oxygen reduction reaction involves 4 electrons with a heterogenous rate constant (k(obs)) of 3x10(5) mol(-1) L s(-1). A linear response range from 0.2 up to 6.4 mg L(-1), with a sensitivity of 4.12 microA L mg(-1) (or 20.65 microA cm(-2) L mg(-1)) and a detection limit of 0.06 mg L(-1) were obtained with this sensor. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation (R.S.D.) was 2.0% for 10 measurements of a solution of 6.4 mg L(-1) oxygen. The sensor was applied to determine oxygen in pond and tap water samples showing to be a promising tool for this purpose.

Amperometric sensor for nitrite using a glassy carbon electrode modified with alternating layers of iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin and cobalt(II) tetrasulfonated phthalocyanine.

The development of a highly sensitive amperometric sensor for nitrite using a glassy carbon electrode modified with alternated layers of iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin (FeT4MPyP) and cobalt(II) tetrasulfonated phthalocyanine (CoTSPc) is described. The modified electrode showed an excellent catalytic activity and stability for the nitrite oxidation decreasing the peak potentials about 200mV toward less positive values and presenting much higher peak currents than those obtained on the bare GC electrode. A linear response range of 0.2-8.6mumoll(-1), with a sensitivity of 0.37muAlmumol(-1) and detection limit of 0.04mumoll(-1) were obtained with this sensor. The repeatability of the proposed sensor, evaluated in term of relative standard deviation, was verified to be 1.4% for 10 measurements of 0.2mumoll(-1) nitrite solution. Interference caused by common ions has been investigated in simulated mixtures containing high concentration level of interfering ions and the sensor was found to be tolerant against these ions. The developed sensor was applied for the nitrite determination in water samples and the results were in agreement with those obtained by a comparative method described in the literature. The average recovery for these samples was 100.1 (+/-0.7)%.

Determination of thickness, dielectric constant of thiol films, and kinetics of adsorption using surface plasmon resonance.

This paper describes the formation of a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) under different concentrations on a gold sensor disk, monitoring in situ and in real time using surface plasmon resonance spectroscopy (SPR). The film thickness and dielectric constant were determined for a fully formed monolayer using one-color approach SPR. The kinetic studies of the film formation in ethanol solution indicated that the self-assembled monolayer is formed in a two-step adsorption process. In this sense, this unpublished route was applied on the basis of a model where many molecules are adsorbed at an initial step and then can be desorbed and/or rearranged to form a perfect monolayer.